7807 Significance of Assessing QTc Interval in Chronic Hypoparathyroidism and its Clinical and Biochemical Correlates

Abstract Disclosure: P.V. Namjoshi: None. S. Saha: None. V. Sharma: None. R. Narang: None. K. Mani: None. R. Goswami: None. Background: Patients with chronic hypoparathyroidism (cHypoPT) and hypocalcemia are at risk of QTc prolongation and life-threatening arrhythmias. Information on clinical and biochemical correlates of QTc in cHypoPT is limited. Design: Observational study in cHypoPT cohort, tertiary-care-center.Materials and methods: Eighty-eight nonsurgical cHypoPT patients (age 44.1±15.4 years, 45 males) were assessed for QTc interval and its possible correlates including arrhythmic symptoms (palpitations/giddiness/syncope), and serum total calcium, phosphorus, 25(OH)D, and iPTH. Results: The mean QTc was 428±34 ms and showed a significant inverse correlation with serum total calcium measured on the same day (r=-0.43, p<0.001). 13.6% of cHypoPT had prolonged QTc. The mean serum total calcium (7.05±1.94 vs. 8.49±1.01 mg/dL, p=0.02) was significantly lower in patients with prolonged QTc. Patients with arrhythmic symptoms had significantly higher mean QTc (p=0.02) and tended to have lower average serum total calcium during follow-up (p=0.06). Multivariable regression showed female gender, higher current age, BMI, and low serum calcium as the significant independent determinants of QTc. For every mg/dL decrease in serum total calcium, QTc increased by 13 ms. Receiver operating characteristic (ROC) analysis revealed serum total calcium at cut-off 8.27 mg/dL discriminated prolonged QTc with area-under-curve being 0.72 [95% CI: 0.51, 0.93]. Conclusion: cHypoPT patients have an increased risk of QTc prolongation which was associated with arrhythmic symptoms, female sex, higher age, BMI, and low serum total calcium. ROC analysis indicated maintaining serum total calcium level of at least 8.27 mg/dL to minimize the risk of prolonged QTc. The study indicates the need for close monitoring of arrhythmic symptoms as well as ECG in cHypoPT patients. Presentation: 6/1/2024